The present invention relates to a flash memory device and a method of fabricating the same and, more particularly, to a flash memory device and a method of fabricating the same, which can solve problems, such as low reliability of the device, which occurs during a drain contact process, by connecting a junction and a bit line without an additional drain contact process.
A flash memory device can be classified into a NOR structure in which a cell is connected in parallel between a bit line and the ground, and a NAND type structure in which a cell is connected in series between a bit line and the ground depending on the structure of a cell array. A cell array of the NAND flash memory device includes cell strings in each of which a plurality of cells for storing data therein is connected in series, and a drain select transistor and a source select transistor connected to opposite ends of the cell strings. Further, the drain select transistor is connected to a drain select line DSL and the source select transistor is connected to a source select line SSL. The drain of the drain select transistor exists in every cell string and is connected to a bit line BL through a drain contact DCT. Further, the sources of all of the source select transistors are connected in parallel to a common source line. A plurality of cells sharing the same word line WL constitute one page. Further, the number of cell strings is equal to the number of bit lines, so the number of drain select transistors and the number of the source select transistors are also equal to the same number.
Recently, with the high integration of NAND flash memory devices, a bowing phenomenon has become more common in which a width at the intermediate depth of a contact hole is widened when forming a drain contact plug since the height of the gate is increased. As a space between the drain contact plugs is narrowed, a short margin is decreased and a short failure is generated between the drain contact plugs.
Further, when forming bit lines on the drain contact plug, the short of the bit lines or a leakage problem is generated due to an overlay failure. Accordingly, during processes of connecting the bit lines and the junctions through the drain contact plugs, several problems in reliability of devices, such as increased resistance, as well as the above problems are generated.